Aging Effect on Foot Dynamics During Unexpected Slips

Slip-induced fall accidents have been recognized as a serious threat to the health of the elderly.The objective of the current study was to investigate the aging effect on the biomechanical reactions of both perturbed foot and unperturbed foot to the unexpected slips. Nineteen younger (mean age: 25.0 years old) and twenty-one older (mean age: 71.2 years old) adults were involved in a laboratory study,in which slippery surface was induced during walking without their awareness.The reactive responses of both slipping foot and unperturbed foot were quantified by optical motion capture system and force platforms.The results indicate a characteristic toe-touch strategy by the unperturbed foot after slip starts. Significant aging effects were found in touch down base of support created by the unperturbed foot. It was concluded that the unperturbed foot is important to facilitate successful recovery from unexpected. Specifically, in order to prevent age-related slip-induced falls, it is important for the unperturbed foot to create sufficient base of support in anterior-posterior direction and to control the base of support in media-lateral direction

Automatic Detection of Slip-Induced Backward Falls

Falls are the leading cause of injury deaths among people 65 years and older. The National Safety Council reported that in 2005, 17,700 Americans met their death by falling, and of these deaths, the majority (over 80%) were people over 65 years of age [1]. It is certainly desirable to avoid the fall accidents altogether through developing a comprehensive fall prevention program [2]. However, in case of unavoidable falls, an effective injury-prevention technology is critical to minimize/reduce fall-related physical injuries. Recently, the concept of wearable airbag [3] emerged as one viable and promising injury-prevention approach

Agreement in Gait Speed from Smartphone and Stopwatch for Five Meter Walk in Laboratory and Clinical Environments

Gait speed is suggested as an independent predictor of post-operative morbidity and mortality in elderly cardiovascular disease (CVD) patients. Society of thoracic surgeons has recently classified gait speed as the only important indicator of health for CVD patients. It has been seen that patients with slow gait speed above 70 years of age, taking more than 6 seconds to walk 5 meters are particularly at high risk for adverse outcomes. Twelve young participants walked in their self-selected, slow and fast speed with five reflective markers at sternum and heels and toes of both feet in laboratory environment. A smartphone was affixed at the pelvis using a smartphone holster. Simultaneously, an examiner used stopwatch to record the elapsed time necessary to cross 5 meter distance. Smartphone based app also computed gait speed. Intra-class correlation coefficients comparing velocities from camera system, smartphone and stopwatch systems were found to be highly reliable (ICC (3,k)=0.82) for slow walking speed. Similarly, fairly good reliability were found for fast (ICC(3,k)=0.70) and normal walking speed (ICC(3,k)=0.66). Five CVD patients were tested in clinical environment with smartphone and its feasibility was assessed for gait speed. This study shows that the smartphone and stopwatch gait speed methods have clinically acceptable agreement for the measurement of gait velocity in the two different environments. The smartphone based reliable measurements could help patients on their own to assess operative risks and health during perioperative period

Comparison of Intra Individual Physiological Sway Complexity from Force Plate and Inertial Measurement Unit

Center of Pressure (COP) is a clinical measure to investigate the effect of sensory input disturbances on postural stability in healthy, old population as well in people suffering from neuromuscular disease. Increased center of pressure velocity and sway area are interpreted as decreased stability or poor balance and are associated with fall risk. Body mounted inertial sensors have shown great promise as an easily implemented clinical measure of balance. The aim of the present study is to investigate if force plate and accelerometer measurements provide similar physiological information when approximate entropy (ApEn) are valuated from the time series. Seven Young and thirteen older individuals (two with fall history and nine without any past fall) participated in this study. There were different complexity measures in healthy young and old participants when both force plate and Inertial Measurement Unit (IMU) were assessed during the same time interval. Thus different control mechanisms are underlying to control trunk sway as measured by IMU than that of COP measured by force plate

Inertial Sensor-Based Variables Are Indicators of Frailty and Adverse Post-Operative Outcomes in Cardiovascular Disease Patients

Cardiovascular disease (CVD) patients with intrinsic cardiac cause for falling have been found to be frail and submissive to morbidity and mortality as post-operative outcomes. In these older CVD patients, gait speed is conjectured by the Society of Thoracic Surgeons (STS) as an independent predictor of post-operative morbidity and mortality. However, this guideline by STS has not been studied adequately with a large sample size; rather it is based largely on expert opinions of cardiac surgeons and researchers. Although one’s gait speed is not completely associated with one’s risk of falls, gait speed is a quick robust measure to classify frail/non-frail CVD patients and undoubtedly frail individuals are more prone to falls. Thus, this study examines the effects of inertial sensor-based quick movement variability characteristics in identifying CVD patients likely to have an adverse post-operative outcome. This study establishes a relationship with gait and postural predictor variables with patient’s post-operative adverse outcomes. Accordingly, inertial sensors embedded inside smartphones are indispensable for the assessment of elderly patients in clinical environments and may be necessary for quick objective assessment. Sixteen elderly CVD patients (Age 76.1 ± 3.6 years) who were scheduled for cardiac surgery the next day were recruited for this study. Based on STS recommendation guidelines, eight of the CVD patients were classified as frail (prone to adverse outcomes with gait speed ≤ 0.833 m/s) and the other eight patients as non-frail (gait speed \u3e 0.833 m/s). Smartphone-derived walking velocity was found to be significantly lower in frail patients than that in non-frail patients (p \u3c 0.01). Mean Center of Pressure (COP) radius (p \u3c 0.01), COP Area (p \u3c 0.01), COP path length (p \u3c 0.05) and mean COP velocity (p \u3c 0.05) were found to be significantly higher in frail patients than that in the non-frail patient group. Nonlinear variability measures such as sample entropy were significantly lower in frail participants in anterior-posterior (p \u3c 0.01) and resultant sway direction (p \u3c 0.01) than in the non-frail group. This study identified numerous postural and movement variability parameters that offer insights into predictive inertial sensor-based variables and post-operative adverse outcomes among CVD patients. In future, smartphone-based clinical measurement systems could serve as a clinical decision support system for assessing patients quickly in the perioperative period

Determination of Stabilogram Diffusion Analysis Coefficients and Invariant Density Analysis Parameters to Understand Postural Stability Associated with Standing on Anti-Fatigue Mats

Prolonged standing has been associated with loss of balance, onset of low back pain symptoms and development of fatigue in lower extremity muscles in working populations. Although so far, it is unknown how individuals’ postural stability is affected by standing on rigid versus cushioned platform but many industries are opting for anti-fatigue mats at workstations to reduce fall and injury related socio-economic cost. The goal of this study is to test SATECH\u27s anti-fatigue mat for its effects on postural stability. A pilot test with seven healthy subjects (25–35 years old) has been conducted with a force plate to obtain kinetics of body when standing on two different platforms. The centers of pressure (COP) position of subjects were determined on rigid and anti-fatigue mats for quiet stance (each trial 60 seconds). In order to understand postural control along with dynamic or stochastic characteristics of the COP, stabilogram diffusion analysis (SDA) and Invariant density analysis methods are used. Subject specific patterns were seen in stabilogram diffusion plots and associated parameters in both conditions. We also found differences in some postural sway SDA parameters with anti-fatigue mats compared to rigid vinyl floor standing with open eyes condition. But no significant differences were found in sway IDA parameters. This work further provides insights whether anti fatigue mats can be helpful to workers involved with prolonged standing tasks

The effects of 10% front load carriage on the likelihood of slips and falls

The objective of the present study was to evaluate if anterior load carriage would increase the likelihood of slips or falls while walking over a slippery floor surface. The study hypothesized that anterior load carriage may alter spatial-temporal characteristics, such as heel contact velocity, walking velocity (i.e., the whole body center-of-mass velocity), and step length, as well as friction demand characteristics at shoe-floor interface. Additionally, the study hypothesized that alterations in these gait parameters may influence slip initiation characteristics while ambulating over a slippery floor surface. Total of 10 subjects participated in the study: 5 younger (18-28 yr old) and 5 older adults (65 and older). A mixture was used to manipulate the coefficient of friction (COF) of the floor surface. All participants were unexpectedly introduced to a slippery surface while walking with and without a load. To evaluate slip severity, slip distance I and II were evaluated to assess whether a subject fell or not. Three-way repeated measure ANOVA (mix-factor design) was performed: Age factor: between-subject, Load and Floor factors: within-subject. Overall, older adults' heel contact velocity was slower while carrying a load. Additionally, all participants exhibited shorter SL while carrying a load. No significant friction demand characteristic differences were observed for all subjects while carrying a 10% front load. The results from the present study suggest that carrying 10% of the body weight in front should not intensify the slip propensity and severity although appears to influence spatial-temporal gait characteristics

A Comparative Study for Performance Evaluation of Sit-to-Stand Task with Body Worn Sensor and Existing Laboratory Methods

Human movement such as sit-to-stand (STS) is one of the most fundamental and essential movement among daily living activities. Elderly who are unable to stand are severely limited in daily activities and rely on others for their care. In the coming next two decades about 20% of US population will be above the age of 65 years, and considering ever-increasing elderly population and health care expenses, the rehabilitation of functionally limited elderly is becoming a topic of greater concern. Clinically STS movement is looked upon with great interest, such as its analysis is meaningful in order to evaluate motor control and stability in elderly patients with functional limitations and may be more helpful than traditional medical evaluations in diagnosing and treating mobility problems in elderly. A few previous research studies describe controlled STS movements with constrains in laboratory environments and have established STS standardized events. A comparative study is presented in this work using and inertial measurement unit (IMU) and existing laboratory based sit-to-stand phases and events. The aims of this study are (1) to define phases and identify events of STS movement based on those previously described, using wireless IMU (2) to test the consistency of these events and phases in total of seven young healthy subjects (ages 25–35 years). We found significant differences in peak flexion angular velocities (p\u3c0.001), peak extension angular velocities (p\u3c0.01) and accelerations at seat-off (p\u3c0.01) between participants when using chair arm rest versus knee as support during rising. Also, we have found significant differences in time events for pre seat off flexion decelerations and post seat off extension angular accelerations with the two different rising supports. Thus these distinct and consistent phases of STS movement using IMU can help identify individuals at fall risk in non-laboratory environments

Fall Risk Assessments Based on Postural and Dynamic Stability Using Inertial Measurement Unit

Objectives: Slip and fall accidents in the workplace are one of the top causes of work related fatalities and injuries. Previous studies have indicated that fall risk was related to postural and dynamic stability. However, the usage of this theoretical relationship was limited by laboratory based measuring instruments. The current study proposed a new method for stability assessment by use of inertial measurement units (IMUs). Methods: Accelerations at different body parts were recorded by the IMUs. Postural and local dynamic stability was assessed from these measures and compared with that computed from the traditional method. Results: The results demonstrated: 1) significant differences between fall prone and healthy groups in IMU assessed dynamic stability; and 2) better power of discrimination with multi stability index assessed by IMUs. Conclusion: The findings can be utilized in the design of a portable screening or monitoring tool for fall risk assessment in various industrial settings

Automatic Detection of Dynamic and Static Activities of the Older Adults Using a Wearable Sensor and Support Vector Machines

Although Support Vector Machines (SVM) are widely used for classifying human motion patterns, their application in the automatic recognition of dynamic and static activities of daily life in the healthy older adults is limited. Using a body mounted wireless inertial measurement unit (IMU), this paper explores the use of an SVM approach for classifying dynamic (walking) and static (sitting, standing and lying) activities of the older adults. Specifically, data formatting and feature extraction methods associated with IMU signals are discussed. To evaluate the performance of the SVM algorithm, the effects of two parameters involved in SVM algorithm—the soft margin constant C and the kernel function parameter —are investigated. The changes associated with adding white-noise and pink-noise on these two parameters along with adding different sources of movement variations (i.e., localized muscle fatigue and mixed activities) are further discussed. The results indicate that the SVM algorithm is capable of keeping high overall accuracy by adjusting the two parameters for dynamic as well as static activities, and may be applied as a tool for automatically identifying dynamic and static activities of daily life in the older adults